Rocs are terrifying, legendary birds renowned for their ability to carry off elephants and other big animals. A typical roc is 30 feet long from beak to tail, with an 80-foot wingspan and weight of up to 8,000 pounds. While their beaks are hooked like an eagle's and designed for slashing and tearing, most rocs prefer to seize prey in their massive, clawed talons and drop them from great heights before feasting on the shattered remains. For this reason, they are often followed by flocks of scavengers like rooks, buzzards, and eagles hoping to steal portions of the roc's messy meals. The roc generally ignores such opportunists, but if the scavengers don't take care, they nevertheless may find themselves accidentally consumed by the feeding roc.

Rocs are equally comfortable over land and sea. While they are capable of sleeping in the air as they soar solo across great ranges in search of food, they generally return home to the mountains to roost and procreate. They prefer rocky crags that are completely inaccessible by terrestrial means, building vast nests of tree trunks and ruined masonry. Once a decade, a mated pair lays a clutch of 3–5 eggs and raises its young. Outside of mating, rocs are extremely antisocial, and may attack others of their kind in vicious aerial battles in order to establish their territorial boundaries. When a nest contains eggs or chicks, parents trade off in their long-ranging flights, with one restricting its wanderings to within a 10-mile radius of the nest.

Rocs are most commonly white but can be a number of different colors, from dark brown or gold to black or blood red. Their massive feathers are highly prized, and their eggs even more so. Due to their scarcity and the high risk involved in harvesting them, a single man-sized roc egg can net 4,000 gp if transported to market undamaged. A roc can be trained as well as any other animal, but its great size makes this a daunting task for most would-be trainers of human size. The same isn't true for giants—particularly cloud and storm giants, who often use trained rocs as guardians for their lairs. Rocs are even large enough to serve as mounts for the most prestigious of giants.

Rocs taken as animal companions by druids or rangers are typically newly hatched birds—a baby roc is the size of a person and ready for flight and hunting within minutes of hatching. Unfortunately for druids seeking animal companions of legendary size, an animal companion roc is limited to Large size—still large enough for a Medium druid or ranger to use the flying beast as a mount.